Although it is well known that some cancer patients commit suicide because of the disease, data on the suicide rate among cancer patients are very soft, only a few reports appearing, with small numbers. For male and female cancer patients in the Connecticut SEER Cancer Registry diagnosed in the decades 1940-49, 1950-59, and 1960-69, death rates due to suicide were derived from analysis of their death certificates. Age and sex-specific population rates of suicide for Connecticut were obtained for the same periods. Within each sex, age-adjusted relative risk of suicide in cancer patients was derived for each decade and over the three decades, as well as relative risks associated with number of years since diagnoses for each decade. Male cancer patients showed a significant excess risk over that of the population during the first several years after diagnosis. Females showed no significant departure from population risk. The data suggested that suicide rates in males during their older years declined over the three decades.